Sen. Tom Carper is upset over a new General Accountability Office finding that the cost of military weapons has risen an inflation-adjusted 38 percent since 2008 and that in just the past year, $31.1 billion has been “flushed away” on “errors and inefficiencies in the manufacturing and design process.”

Carper, who is chairman of the Senate Subcommittee on Federal Financial Management, Government Information, Federal Services and International Security, called the increase in spending on the Pentagon’s 96 major weapons programs “alarming,” and said the $31.1 billion GAO said had been wasted was “clearly unacceptable.”

“The Department of Defense must do a better job of efficiently developing our nation’s largest and most costly weapons,” Carper said in a statement released today. “These cost overruns not only waste taxpayer money, but also put additional strain on a military budget that is already stretched thin. If we are going to have any hope of strengthening our military and achieving a balanced budget down the line, we’ve got to reverse the trend of growing weapons system cost overruns.”

GAO said most of 2011′s cost growth centered around the troubled F-35 Joint Strike Fighter program. The JSF is being developed on three different tracks: a conventional takeoff/landing jet for the Air Force; a short takeoff/vertical landing jet for the Marine Corps; and a carrier-capable jet for the Navy.

Despite more than a decade in development, GAO found that “manufacturing inefficiencies persist, primarily driven by parts shortages, parts quality issues, and technical changes arising from discoveries during test events, indicating that the aircraft’s design and production processes may still lack the maturity needed to efficiently produce aircraft at planned rates.”

Of interest to Delaware’s Air Guard community — and a good example of how development costs can increase unexpectedly — GAO found that the C-130 Avionics Modernization Program, which entered production in 2010, “experienced a greater number of design changes than anticipated in fiscal year 2011″ and that new software was added to address deficiencies found in testing. Testors found that “the core avionics were not well adapted to the C-130′s tactical missions and crew workload needed to be reduced during airdrop and low-level operations.” New software testing begins in August.

In addition, the full-rate production decision has slipped from February 2013 to September 2014 to give a second contractor time to get familiar with the AMP kit installation and fairly compete for the full-rate production contract.